Mechanisms of host defenses in herpes infection of the nervous system are being studied from multiple approaches. Passive transfer studies to determine the timing and site of effectiveness are being conducted in mice. Cell recruitment to the site of nervous system infection is being studied by histopathologic assessment of lesion evolution. In addition, the impact of evolving infection on the blood brain barrier is being evaluated to determine when the barrier is destroyed. The basis of genetically determined resistance to herpes viruses will be examined by studying the kinetics of antibody production, macrophage restriction of virus replication, viral tissue titers during acute infection, the effect of adoptive transfer and other studies of cell mediated immunity.